1. Field of the Invention
The present invention relates generally to a magnetic recording head motion translation apparatus, and more particularly to a linear motion translation apparatus which can replicate the radial arc motion of a magnetic recording head which is being driven by a rotary actuator of a disk drive system.
2. Discussion of the Prior Art
The process of selecting components for use in a prototype hard disk drive system requires the analysis of a large quantity of magnetic media and magnetic recording heads. Until a particular combination is selected for use in the prototype system, the different types of heads and media will be tested for quality, as well as system compatibility. There are a number of different evaluation systems which are used for these tests, such as certifiers, glide-height testers, and spin testers. These head/media evaluation systems are typically linear drive based systems, which use a linear motor, such as a voice coil motor or stepper motor in combination with a lead screw, to move the magnetic recording head across the surface of the media.
Linear drive based evaluation systems have proved to be adequate for testing heads and media in the past because of the relatively large size of the magnetic recording heads, the relatively slow speed at which the heads could be moved across the media, and the limited requirements of prototype drive designers. In addition, many of the hard disk drive systems which have been developed have used linear drive units, or actuators, to move the heads within the drives. Thus, the ability to test the components on the evaluation system in a manner similar to how the components would be used in the disk drive was desirable, thereby making linear drive based systems acceptable.
In an effort to meet the demand for higher storage capacity, smaller, and faster disk drives, there has been a movement among drive designers to decrease the size of disk drives, increase their storage capacity, and increase their average access time. Accordingly, disk drive technology has been moving away from larger recording heads and linear actuators, which are slower, in favor of smaller heads and rotary actuators, which are faster. Evaluation systems, however, unlike the drives which the systems were designed to test, have continued to be designed as linear drive based systems, thereby creating a problem which is addressed by the present invention.
A hard disk drive magnetic recording head is typically comprised of two flat rails, running the length of the head, and a magnetic coil, which is located at the rear end of the head. A small portion of the rails, toward the front end of the head, is sloped upward so as to make each rail have a bottom surface like a snow ski. When the disk drive is turned off, the head, or bottom surface of each rail, lies flat on the surface of the media. The media will begin to spin when the disk drive is turned on, causing air travelling on the surface of the media to be forced under the sloped portion of each rail, thereby causing the head to be lifted off the surface of the media onto a small cushion of air. In other words, the combination of the sloped portion of the head and the rapidly moving air creates a wedge for lifting the head off the surface of the media. The head will normally continue to glide on a 8 to 14 micro-inch cushion of air while the media continues to spin.
An adequate wedge will be maintained as long as the head is kept relatively perpendicular to the direction of the air flow over the surface of the media. An "adequate wedge" is a wedge sufficient to lift the head off the media and keep the head from contacting the media during operation of the drive. Maintaining an adequate wedge in a linear actuator based disk drive system has not been a significant problem because the head is moved perpendicular to the direction of the air flow at all times. However, when a head is moved across the media in a radial arc, such as that created by a rotary actuator, an adequate wedge can be difficult to maintain. Almost any fluctuation in the wedge can cause the head to come into contact with the surface of the media (commonly referred to as a head crash), and result in a loss of data or even the destruction of the disk drive.
Hard disk drive magnetic recording heads could be redesigned so as to prevent any possibility of losing an adequate wedge. However, the magnetic recording head is one of the most expensive and sensitive components in a disk drive, and any significant change in its design would require a significant amount of engineering design and test time, as well as increased production costs. In addition, if redesigning the head was the most practical solution for assuring that an adequate wedge is maintained at all times, the head would have to be redesigned every time the movement of the head over the surface of the media was modified. Due to the present reliability of currently available heads and the impracticality of redesigning the heads for each new drive design, disk drive manufacturers would prefer to be able to use currently available heads in their new disk drive systems. Thus, a need exists for a head/media evaluation system for testing currently available heads which will allow the operator to readily modify the path that a head will follow across the media.
A number of head/media evaluation systems have recently been made available which utilize a rotary based actuator to move the magnetic recording head across the surface of the media. Rotary drive based evaluation systems are being developed because presently available linear drive based evaluation systems are limited to only being able to move the head across the media along a linear path. Although rotary drive based systems can accurately move a head in a radial arc motion across the surface of the media, such systems can not be readily modified to replicate a different radial arc head motion, or a linear head motion. Accordingly, the present invention describes a magnetic recording head motion translation apparatus, for use in head/media evaluation systems, which can be readily modified to change the path that the head follows over the surface of the media.